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Is Povidone-Iodine (PVP-I) deactivated in the presence of blood and organic material?
The short answer is “theoretically, yes; practically, no”.
Polyvinylpyrrolidone (PVP) is a polymer used in many applications. In the first half of the 20th century, PVP was used as a blood plasma expander for trauma victims. Today, it’s used as a binder in many pharmaceutical tablets. It’s also used in personal care products such as shampoos, toothpastes, and contact lens solutions.
When combined, PVP and iodine form Povidone-Iodine (PVP-I); a water-soluble complex consisting of 10% iodine and 90% PVP. A solution that is 10% Povidone-Iodine, in turn, contains 1% iodine “available” for killing microorganisms. Commercially, PVP-I is commonly known under the trade name of Betadine. Many generics now exist and based on years of use, solutions containing between 5% - 10% PVP-I (containing between 0.5% - 1% available iodine) are generally recognized by the FDA to be safe and effective for preparation of the skin prior to surgery.
A number of articles have stated that PVP-I is neutralized or inactivated in the presence of blood, serum, and other protein-rich biomaterial. However, a closer look at the data and cited literature indicates that from a practical perspective, this assertion is simply Urban Legend.
The reference most commonly used to support the assertion that PVP-I is neutralized or inactivated in the presence of blood, serum, and other protein-rich biomaterial is…
Chaiyakunapruk N, Veenstra DL, Lipsky BA, and Saint S. Chlorhexidine compared with povidone-iodine solution for vascular catheter-site care: a meta-analysis. Ann Intern Med. 2002; 136; 792-801 which is available at http://www.annals.org/cgi/reprint/136/11/792.pdf.
The exact quote appears at the top of page 799. It states “blood, serum, and other protein-rich biomaterials can deactivate the microbicidal effect of povidone-iodine”, and two references are given to support this assertion:
- Gottardi W. Iodine and iodine compounds. In: Block SS, ed. Disinfection, Sterilization, and Preservation. 4th ed. Philadelphia: Lea & Febiger; 1991:151-66.
- Zamora JL, Price MF, Chuang P, Gentry LO. Inhibition of povidone iodine’s bactericidal activity by common organic substances: an experimental study. Surgery. 1985;98:25-9.
First, Chaiyakunapruk et al. states that “protein-rich biomaterials can deactivate the microbicidal effect of povidone-iodine”; they don’t say that PVP-I is always deactivate by these materials. Second, the following is an excerpt from Gottardi (highlights and underlines provided for emphasis):
Quantitative investigations into the consumption of iodine (and other oxidizing substances) with blood are distinguished by poor reproducibility, which can be attributed to the different reactions of iodine with SH groups [equation (16a, b)]. In practice, no substantial decrease in the bactericidal efficacy of 10% povidone-iodine preparations is likely with body fluids having a composition similar to plasma (volume substrate/volume 10% povidone-iodine < 0.6). However, contamination by 25% or more whole blood should be avoided.
Point #1: Studies that look at this issue are difficult to carry out properly and as a result, their results should be suspect.
Point #2: While true in theory (i.e., oxidizing agents including Povidone-Iodine are consumed in the presence of organic material), in practice, there is so much iodine present, that it doesn’t matter. I would submit that if the field being prepped is being “contaminated” with enough blood to dilute the prepping solution by 25%, the clinicians on the case have more to worry about than how effectively they’re prepping the patient.
Zamora et al. looked at the effects of diluting a 10% Povidone-Iodine formulation with various organic materials; specifically fat, pus, and blood. The results of their study are provided below (screen captures from the actual article).
In the case of fat, the Povidone-Iodine solution was able to be diluted from 10% to 0.1% (a 100X dilution), and still only one of the bacteria tested were viable; the remaining species was unable to grow.
In the case of pus, the Povidone-Iodine solution was able to be diluted from 10% to 1% (a 10X dilution), and none of the bacteria tested were viable.
In the case of blood, the Povidone-Iodine solution was able to be diluted from 10% to 5% (a 1X dilution), and still only two of the bacteria tested were viable; the remaining species were unable to grow.
These results are consistent with Gottardi’s assertion that “In practice, no substantial decrease in the bactericidal efficacy of 10% Povidone-Iodine preparations is likely with body fluids having a composition similar to plasma”.
Other studies have been published on this subject indicating differing results. Below are several such studies with their accompanying abstracts (highlights and underlines provided for emphasis). Both studies concluded that chlorhexidine gluconate (CHG) was more adversely affected by the presence of serum than Povidone-Iodine (PVP-I).
Ishizaka T, Goto S. Influence of serum on antibacterial activity of disinfectants and evaluation of disinfectant testing methods. J Nippon Hosp Pharm Assoc Sci Ed 1978. 3(4); 208-14.
Influence of serum on antibacterial activity of disinfectants and evaluation of disinfectant testing methods, ie, phenol coefficient method and minimum inhibitory concentration method, were studied. Changes in the effect of various disinfectants such as phenol (I), saponated cresol (II) solution, povidone-iodine (III) benzethonium chloride (IV) and chlorhexidine (V) by serum were determined against various strains of Staphylococcus aureus, Salmonella typhi, E. coli, Klebsiella pneumoniae, Serratia marcescens, Pseudomonas aeruginosa, P. maltophilia, P. cepacia and Achromobacter xylosoxidans . The antibacterial activity of I, II and III [PVP-I] was reduced very slightly after serum was added, but that of serum added to IV and V [CHG] decreased remarkably. The bactericidal effect of serum added disinfectants one hr after contact with bacteria was reduced by 25 to 50% 24 hr later. The antibacterial effect of disinfectants determined by the MIC method showed a considerable difference from the effect determined by the phenol coefficient method.
Yoneyama A, Shimizu M, Tabata M,Yashiro J, Takata T, Hikida M. In vitro short-time killing activity of povidone-iodine (Isodine (R) gargle) in the presence of oral organic matter. Dermatology (Basel) 2006. 212(1): 103-108.
In order to estimate the clinical efficacy of a povidone-iodine oral antiseptic (PVP-I) on oral bacterial infectious diseases, we studied the effect of oral organic matter on the in vitro killing activity of PVP-I. In addition, we compared the in vitro short-time killing activity of PVP-I with those of other oral antiseptics using mouth-washing and gargling samples collected from healthy volunteers. When any of the mouth-washing and gargling samples was used, the standard (0.23-0.47%) or lower concentrations of PVP-I killed methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa, including multidrug-resistant strains, within 15-60 s in the presence of oral organic matter. 0.02% benzethonium chloride (BEC) and 0.002% chlorhexidine gluconate (CHG) did not show effects against MRSA and P. aeruginosa (including multidrug-resistant strains) in mouth-washing and gargling samples even after 60 s. The above-mentioned results show that the in vitro killing activity of the standard concentration of PVP-I was hardly affected by the oral organic matter and that a mouth-washing or gargling solution containing PVP-I has a stronger bactericidal activity than BEC and CHG. Although mouthwashing and gargling samples were obtained from healthy individuals in this study, PVP-I may be used for protection against infections in patients with various diseases, if proper concentrations and usage are encouraged. Copyright (c) 2006 S. Karger AG, Basel.
The activity/effectiveness of any chemical entity is lessened with dilution. The real question is “Does the degree of anticipated dilution matter in practice. In the case of both chlorhexidine gluconate and Povidone-Iodine, based on the data reported above, the answer to this question is unequivocally “no”.
In practice, no substantial decrease in the bactericidal efficacy of Povidone-Iodine preparations is likely with body fluids having a composition similar to plasma.
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